Scientists discover two new high‑pressure ice forms that may exist in Neptune and Uranus

Scientists have discovered two previously unknown crystalline forms of ice by subjecting liquid water to pressures exceeding 10 million atmospheres in laboratory experiments. The high‑pressure conditions, achieved using diamond‑anvil cells and laser heating, produced ice phases that differ from the familiar hexagonal ice Ih found on Earth. Detailed X‑ray diffraction and Raman spectroscopy revealed distinct lattice arrangements, indicating that the molecules are packed more tightly and exhibit new symmetry properties.

The findings are relevant to the interiors of the ice giants Neptune and Uranus, where temperatures of several hundred kelvin and pressures of several megabars are expected. In these environments, water, ammonia, and methane are thought to coexist under extreme conditions, potentially forming exotic ices that influence the planets’ magnetic fields, heat transport, and overall structure. By mapping the phase diagram of water at such pressures, researchers can refine models of planetary interiors and improve predictions of their evolution.

These experiments underscore the importance of laboratory analogues for understanding planetary science. The newly identified ice phases provide critical data for interpreting observations from missions to the outer planets and for guiding future studies of matter under extreme conditions.